1. Field of the Invention
This invention relates to the co-processing of residual oil and coal. More particularly, it relates to a process for the production of light distillates and fuel oil from residual oil and coal. This invention especially relates to the processing of residual oil and coal in the presence of a catalytic cracking catalyst.
2. Description of the Prior Art
Petroleum has been utilized heretofore as a major source of energy, particularly because of its relatively low cost and its availability in liquid form which permitted ease of transportation and ultimate use. This relatively clean burning energy source presents a minimum of disposal problems and thus has found wide spread use throughout the world. Natural gas is a fuel which has also been utilized as a particularly useful form of energy but its gaseous form has limited its transportability and hence it has not found the world wide use that petroleum has. Recent economic and political developments have led to increasingly high purchase prices for both of these products. In addition, the high cost of energy from petroleum and natural gas as well as their potentially limited availability has led to investigation of alternate sources of energy such as oil shale and tar sands. There has recently been an increased interest in coal as a major energy source. Reserves of coal are far greater than the known reserves of all other mineral fuels (petroleum, natural gas, oil shale and tar sands) combined. Since coal is a solid fuel and when burned in this form requires disposition of residual ash, its use as a major energy source is not as desirable as either petroleum or natural gas. However, processes have been and are being developed to convert coal into both liquified and gaseous fuels which will increase its desirability as a useful energy source. Although these conversion processes have not proven economical heretofore, the increasing cost of conventional energy sources make these conversion techniques more and more attractive.
Coal liquefication and gasification processes developed heretofore utilize a wide variety of techniques including thermal and catalytic conversion, non-hydrogenative and hydrogenative conversion and various combinations thereof. Patent art in this area includes the following:
U.S. Pat. No. 3,870,621 of Arnold, et al. discloses contacting a liquid phase of a petroleum residual oil with finely divided coal in a fixed or moving bed at a temperature in the range of 700.degree.-900.degree. F. to produce cracked products from the oil and hydrocarbons from the coal which are fractionated to produce a heavy recycle stream and lighter products. The solid char recovered as a product from the contacting zone can find use as a high quality solid fuel.
U.S. Pat. No. 4,108,758 of Schoennagel, et al. discloses a process for obtaining liquid fuels from coal which involves the solubilizing of coal in a fluid catalytic cracked residual oil to form a solvated coal solution phase and an ash solid phase. The two phase admixture is fluid catalytic cracked to produce a hydrocarbon phase and a catalyst-ash solids phase. The catalyst-ash solids phase is treated in a catalyst regeneration zone whereby entrained ash solids are removed from the flue gas effluent from the catalyst regenerator. The solvated coal admixture is mixed with gas oil and introduced into a conventional fluid catalytic cracking unit.
U.S. Pat. No. 4,152,244 of Raichle, et al. relates to the production of hydrocarbon oils by the hydrocracking of finely ground coal. The coal is slurried, optionally with a catalyst, in a mixture of middle or heavy oil recycled from the recovery section of the process. The slurry is heated together with hydrogen at elevated temperature and pressure to produce gas, gasoline, middle distillates and heavy oil. The solids from the bottoms product are recovered for conversion in a gasifier to produce synthesis gas.
U.S. Pat. No. 4,169,038 of Metrailer et al. discloses a combination process of hydroconversion, fluid coking and gasification. A liquid-comprising carbonaceous charge stock, which may be a slurry of coal in petroleum residua, is subject to hydroconversion in the presence of a catalyst of solid carbonaceous fines recovered from the downstream gasifier. A heavy oil fraction, recovered from the hydrocarbonaceous oil product of the hydroconversion, is subject to fluid coking to form additional coke which in turn is introduced into a gasification zone with steam and a molecular-oxygen containing gas to produce a synthesis gas containing hydrogen. Solid carbonaceous fines are recovered from the gasifier and recycled to the hydroconversion zone for use therein as the catalyst.
Other prior art processes disclose catalytic hydroconversion of coal admixed with oil. These processes include those disclosed in U.S. Pat. Nos. 2,377,728 of Thomas; 4,054,504 of Chervenak, et al.; 4,111,787 of Aldridge, et al. and 4,132,627 of Leas, as well as in "The Use of Heavy Oils to Upgrade Coal", by Moschopedis, et al. presented at the 30th Canadian Chemical Engineering Conference in October, 1980.
Although most of the prior art coal conversion processes employ hydrogen, several of those discussed herein, U.S. Pat. Nos. 3,870,621 of Arnold, et al. and 4,108,758 of Schoennagel, et al. do not employ hydrogen in the conversion step. However, in Arnold, et al. the heavy feed is essentially catalytically cracked, utilizing solid coal particles as the catalyst under temperature conditions of 700.degree.-900.degree. F., a pressure between 10 and 100 psig and a space velocity of 0.1 to 3.0 lbs. of oil per hour per pound of coal. The liquid product is fractionated to a light fraction recovered as the product with the higher boiling fraction recycled to the contacting zone. A solid char is withdrawn from the bed of coal and is utilized as solid fuel. In Schoennagel, et al. a mixture of residual oil and coal is admixed with gas oil and introduced into a conventional catalytic cracking reactor to produce the conventional liquid products obtained in catalytic cracking. The ash from the coal is recovered in the gaseous effluent from the regenerator vessel.
It is an object of this invention to provide a process for converting mixtures of petroleum residua and coal to useful products under relatively mild process conditions.
It is another object of this invention to provide a process for producing normally gaseous hydrocarbons, atmospheric distillates and vacuum distillates from residual oils co-processed with coal.
It is a further object of this invention to convert petroleum residual oil and coal to products including light olefinic hydrocarbons, light distillate in the gasoline boiling range, light and heavy gas oils, residual oil having reduced metals content and low or intermediate BTU fuel gas.